linux-kernel - RE: [PATCH net-next 2/2] net: stmmac: Add callbacks for DWC xpcs Energy Efficient Ethernet

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Date:   Wed, 19 May 2021 02:27:15 +0000
From:   "Sit, Michael Wei Hong" <michael.wei.hong.sit@...el.com>
To:     Russell King <linux@...linux.org.uk>
CC:     "Jose.Abreu@...opsys.com" <Jose.Abreu@...opsys.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "Voon, Weifeng" <weifeng.voon@...el.com>,
        "Ong, Boon Leong" <boon.leong.ong@...el.com>,
        "Tan, Tee Min" <tee.min.tan@...el.com>,
        "vee.khee.wong@...ux.intel.com" <vee.khee.wong@...ux.intel.com>,
        "Wong, Vee Khee" <vee.khee.wong@...el.com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next 2/2] net: stmmac: Add callbacks for DWC xpcs
 Energy Efficient Ethernet



> -----Original Message-----
> From: Russell King <linux@...linux.org.uk>
> Sent: Tuesday, 18 May, 2021 6:06 PM
> To: Sit, Michael Wei Hong <michael.wei.hong.sit@...el.com>
> Cc: Jose.Abreu@...opsys.com; andrew@...n.ch;
> hkallweit1@...il.com; kuba@...nel.org;
> netdev@...r.kernel.org; peppe.cavallaro@...com;
> alexandre.torgue@...s.st.com; davem@...emloft.net;
> mcoquelin.stm32@...il.com; Voon, Weifeng
> <weifeng.voon@...el.com>; Ong, Boon Leong
> <boon.leong.ong@...el.com>; Tan, Tee Min
> <tee.min.tan@...el.com>; vee.khee.wong@...ux.intel.com;
> Wong, Vee Khee <vee.khee.wong@...el.com>; linux-stm32@st-
> md-mailman.stormreply.com; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH net-next 2/2] net: stmmac: Add callbacks for
> DWC xpcs Energy Efficient Ethernet
> 
> On Mon, May 17, 2021 at 11:37:12AM +0000, Sit, Michael Wei
> Hong wrote:
> > > From: Russell King <linux@...linux.org.uk>
> > >
> > > On Mon, May 17, 2021 at 05:43:32PM +0800, Michael Sit Wei
> Hong
> > > wrote:
> > > > Link xpcs callback functions for MAC to configure the xpcs
> EEE
> > > feature.
> > > >
> > > > The clk_eee frequency is used to calculate the
> > > MULT_FACT_100NS. This
> > > > is to adjust the clock tic closer to 100ns.
> > > >
> > > > Signed-off-by: Michael Sit Wei Hong
> > > <michael.wei.hong.sit@...el.com>
> > >
> > > What is the initial state of the EEE configuration before the
> first
> > > call to stmmac_ethtool_op_set_eee()? Does it reflect the
> default EEE
> > > settings?
> >
> > The register values before the first call are the default reset
> values
> > in the registers. The reset values assumes the clk_eee_i time
> period
> > is 10ns, Hence, the reset value is set to 9.
> > According to the register description, This value should be
> programmed
> > such that the clk_eee_i_time_period * (MULT_FACT_100NS + 1)
> should be
> > within 80 ns to 120 ns.
> >
> > Since we are using a fixed 19.2MHz clk_eee, which is 52ns, we
> are
> > setting the value to 1.
> 
> Does that hardware default configuration match what is returned
> by ethtool --show-eee ?

May I know what is the hardware default configuration that is expected
to be returned by ethtool --show-eee?
The MULT_FACT_100NS value is an internal register setting not meant
to be exposed to userspace, and only relevant when EEE is enabled.
> 
> --
> RMK's Patch system:
> https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at
> last!